1. Field Of The Invention
This invention relates to a gas fired absorption air cooling and heating system which provides a simplified process and apparatus for both cooling and heating, in particular, a gas fired absorption process and apparatus in which the absorber, outdoor coil and condenser are shunted out of the system in a heating mode of operation.
2. Description of the Prior Art
Absorption cooling systems are well established in the prior art. In such systems, refrigerant vapor is absorbed in an absorber. The resulting absorbent-refrigerant solution is circulated to a generator in which it is heated. The refrigerant is separated from the absorbent-refrigerant solution and condensed, after which it is recycled to an evaporator in which it is vaporized to be reabsorbed in the absorber and begin the cycle again.
Lithium bromide absorption air conditioner/heaters have been applied in the past to small commercial and residential applications. In these low capacity applications, the refrigerant, which is water, is boiled in an evaporator. The evaporator, in the form of a coil, provides the cooling for the supply air directly. The coil consists of a bank of tubes through which the water, at very low pressures, from about 6 to about 9 millimeters of water column absolute, is flowing. The water boils and delivers a cooling effect to an air stream which flows on the outside of the tube bank. The outside surface of these tubes is generally finned in order to promote heat transfer from the air stream.
In order to allow these systems to provide heating through the cooling cycle, two known systems can be used. In the first system, the evaporator serves as an absorber, with the heat of absorption being rejected to the air stream of spatial air flowing around the coils of the evaporator. However, to make an evaporator operate in this manner is technically cumbersome. A simpler approach is to eliminate the condenser from the cycle and pass refrigerant vapor directly from the generator to the coil. In this case, the refrigerant vapor, preferably water vapor, condenses in the evaporator and is then returned to the generator. In effect, the evaporator is used for "steam heating" and the heating effect is not sensitive to the configuration of the coil in the evaporator.
However, one disadvantage of this steam heating cycle is that any pump in the absorption system must handle any output of the evaporator as well as the dilute absorbent solution returning from the absorber, both of which are mixed together before passing through the pump. During a cooling mode of operation, the solution in the pump will be fairly cool. However, in a heating mode of operation, a steam heating cycle produces a significant amount of condensed refrigerant exiting the evaporator. Thus, absorbent solution passing through the absorber will not be diluted, but rather will mix with the refrigerant condensate in the pump which mixing results in the release of a significant amount of heat due to the heat of solution, producing a hot dilute absorbent solution which can adversely affect pump life.
Also of concern is the efficiency of such a system. The heat of solution liberated when the concentrated absorbent solution and the refrigerant condensate are mixed is heat which is returned to the generator. Mixing these solutions in the pump and returning the resulting hot solution to the generator may increase jacket losses and decrease the overall efficiency of the system in the heating mode of operation. Even if insulation is properly applied to prevent such jacket losses, the dilute absorbent solution returned to the generator will be hotter than usual, thereby increasing overall generator temperatures. The increased generator temperatures result in a reduction in heat transfer from the burner in the generator and, thus, the overall efficiency of the system is reduced. In addition, higher generator temperatures tend to significantly increase corrosion rates within the system.
U.S. Pat. No. 4,178,989 teaches a solar powered lithium bromide absorption cooling/heating system in which the refrigerant is used as the heating medium for the heating cycle, bypassing the absorber and undergoing condensation in the heat exchanger between the condenser and the absorber. This patent teaches separation of the refrigerant from the solvent and storage of the solvent in an absorber and reservoir which is bypassed in the heating mode while the refrigerant may be stored in a separate reservoir interposed between the condenser and the expansion valve.